Royal Astronomical Society. 57 



instrument ; viz. that it works with no apparent error in collimation, 

 nor level error, but correcting as occasion may require for azimuthal 

 deviation. With the exception, therefore, of minute differences in the 

 right ascensions of the stars by which the clock-errors were deter- 

 mined, and some trifling optical defects, I conclude that nothing of 

 importance can be urged against the mean of all the results. In- 

 deed, all the observations respecting the chronometrical comparisons 

 are plain and straightforward matters of fact in conjunction with the 

 transit observations, as recorded in the observation books." 



The error in the former assumed longitude being now fully con- 

 firmed by so many chronometrical results, it was resolved to connect 

 in a more accurate manner than before the position of Aylesbury 

 spire with that of the observatory at Hartwell by actual measurement 

 and triangulation ; since it was possible that an error might have oc- 

 curred so as to have caused the discrepancy observed between the 

 chronometrical longitude and that obtained by the Trigonometrical 

 Survey. This was done in April 1840, and the result was nearly iden- 

 tical with that previously deduced by means of the county survey. 



As there is a considerable error in the longitude of this spire as 

 given in the third edition of the Requisite Tables, Mr. Yolland, of the 

 Ordnance Map Office, very kindly undertook the recomputation of its 

 geographical position from the original data of the Trigonometrical 

 Survey, and found it to be as follows : — t „ 



Latitude '. . 5149 10 North. 



Longitude 48 50-15 West. 



In time 3 m 15 s< 34 



From this corrected position of the spire, we have the following 

 for the position of the observatory at Hartwell : — 



Latitude 51° 48' 14"-8 North. 



Longitude 3 m 22 s -57 West. 



Final results for difference of meridians : — m s 



By the chronometrical determinations 3 24*26 



By Aylesbury spire, as determined by the Trigonome- 1 ., 99 .k 7 

 trical Survey J J 



Difference 1*69 



II. Observations of the Beginning and Termination of the Solar 

 Eclipse of July 18, 1841, at Aberdeen. By Charles Crombie, Esq. 

 Communicated by George Innes, Esq. 



The eclipse was observed in the garden attached to Mr. Crombie's 

 residence, which is a short distance from the Marischal College. 

 The instrument used was a 2£ feet achromatic telescope, with a 

 power of about thirty-six ; and the times were taken with a pocket 

 chronometer, whose rate was determined by two comparisons with a 

 clock belonging to Mr. Innes, and the error by several altitudes of 

 the sun. 



The Aberdeen mean solar times of the beginning and ending of 

 the eclipse, resulting from the observations, are — 



h m s 



For the beginning 2 17 48*7 



And for the ending 2 58 10'2 



